Replace RSC streaming with /api/ai Route Handler for Docker reliability.

Server Actions + createStreamableValue kept failing in production; fetch-based text stream avoids RSC serialization issues and shows readable error messages.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/ai/client-stream.ts

@@ -0,0 +1,34 @@
+import type { AiRequestBody } from "@/lib/ai/types";
+
+export async function streamAiCompletion(
+  body: AiRequestBody,
+  onUpdate: (text: string) => void,
+): Promise<void> {
+  const res = await fetch("/api/ai", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(body),
+  });
+
+  if (!res.ok) {
+    const message = (await res.text()).trim();
+    throw new Error(message || `AI 请求失败 (${res.status})`);
+  }
+
+  if (!res.body) {
+    throw new Error("AI 响应为空");
+  }
+
+  const reader = res.body.getReader();
+  const decoder = new TextDecoder();
+  let text = "";
+
+  while (true) {
+    const { done, value } = await reader.read();
+    if (done) {
+      break;
+    }
+    text += decoder.decode(value, { stream: true });
+    onUpdate(text);
+  }
+}